New ways to track verification proofs for source code of Ethereum's earliest contracts

Yesterday I posted about verifying Vitalik's first token contract and got a great response. A few people asked how to follow along as more proofs are published, so I set up two places to track them:

• GitHub: awesome-ethereum-proofs - each proof has its own repo with a reproducible verification script
• Web: ethereumhistory.com/proofs - browse all verified contracts with deployment dates, compiler versions, and methodology

Most contracts deployed in August 2015 have no verified source on Etherscan. The compilers are too old for automated tools, source code was hosted on Pastebin links that expired years ago, and some contracts used languages Etherscan doesn't even support (Serpent, LLL). So I've been doing it manually - testing every early compiler version against on-chain bytecode until I get a byte-for-byte match.

Since the Vitalik post, here are 4 new proofs:

"Test" - First Executable Contract (Aug 7, 2015, block 48,643) The earliest contract with executable code on Ethereum mainnet. Compiled with soljson v0.1.1, the first publicly available Solidity compiler release. Just 8 days after mainnet launch.

Hello World Greeter (Aug 7, 2015, block 48,681) Ethereum's "Hello World" moment. Deployed 38 blocks after the first executable contract, same day, same compiler. Based on the greeter tutorial that shipped with the early Ethereum documentation.

EarlyChainLetter10ETH (Aug 8, 2015, block 49,931) A chain letter pyramid contract from day 2 of smart contract deployment. One of the first attempts at a financial game on Ethereum. Participants sent 10 ETH to join, and the contract would pay out earlier participants as new ones joined.

FunDistributor (Aug 10, 2015, block 62,632) A "king of the hill" behavioral economics experiment. Send more than 1% of the contract's balance to become the receiver. If nobody touches the contract for 200+ blocks (~45 min), the current receiver gets paid out. The original source was on Pastebin (link expired) - had to reconstruct it entirely from bytecode. Interesting discrepancy: the Reddit announcement said the payout was 25% of the balance, but the verified code shows this.balance / 3 (33.3%).

Some things I've learned doing this:

• Operand order matters in solc 0.1.1. msg.value * 100 and 100 * msg.value produce different bytecode because the compiler evaluates right-to-left.
• The private keyword existed in solc 0.1.1 but was almost never used. FunDistributor is one of the earliest known uses.
• Solidity function declaration order affects optimizer output. Changing the order of functions in the source can completely change the compiled bytecode.

There are 11 proofs so far covering contracts from Aug 2015 through Apr 2016, including Serpent, Solidity, and contracts by Vitalik and Gavin Wood. More coming as I work through the earliest blocks.

If you know of any early contracts with lost source code, I'd love to hear about them.